1. Field of the Invention
This invention relates to a method and device for reforming the end of a plastic pipe to form a flange thereon and to an improved tubular member lined with a plastic pipe liner having such a flanged end.
2. Description of the Prior Art
The installation of plastic pipe liners within tubular members achieves several desirable results. For instance, such liners are used to repair pipelines which have developed cracks or leak points through which conveyed fluid is lost. Such liners are also used to protect metal pipelines from internal corrosion resulting from the corrosive nature of the conveyed fluid. In the case of oil field pipe, many of the fluids transported for completion, stimulation or production have a detrimental effect on the metal from which the pipe is constructed.
The plastic pipe liners which are installed within metal tubular members are usually thermoplastic materials. These materials can be heated to a temperature and for a time sufficient to render the material to a malleable state so that the material can then be formed to the desired shape. The term "plastic" is intended to include, for example polyethylene, polyvinyl chloride, polyvinyl chloride-acetate, polystyrene, and the like.
In the case of flanged metal pipelines, various adapters have been provided in the past for joining sections of the pipeline as well as the associated sections of plastic liners. In one prior art technique, the adapters were fused onto the plastic liner ends which protruded from the section of metallic pipeline. Since the adapters were of a fixed length, it was necessary to accurately calculate the expansion and contraction characteristics of the plastic liner installed within the section of metallic pipeline to prevent the adapter from being pulled out of position upon contraction of the liner.
In other prior art techniques, an exposed portion of the plastic liner was bent backward at an angle or "flared" to form a flange on the plastic liner. U.S. Pat. No. 3,142,868 to Blount, issued Aug. 4, 1964, is typical of this type prior art approach in which a mechanical device is utilized to flare a liner end extending from a tubular member. The process also involved heating, supporting and cooling the flared end.
The prior art techniques all suffer from the shortcoming that the liner flanged end could be drawn longitudinally inward into the interior of the tubular member upon contraction of the liner material. Flaring also created thin wall regions at the flanged end which were subject to shearing and failure.
The present invention has as its object to provide a method and device for forming a flange on an end of a plastic pipe liner which resists the tendency to contract, once installed, and be pulled into the interior of the surrounding tubular member.
Another object of the invention is to provide a simple and economical method for forming such a flange on the plastic pipe liner used to line a tubular member.
Another object of the invention is to provide an improved reinforced disc for reinforcing the plastic pipe liner flange to prevent subsequent movement of the plastic pipe liner flange.